We have established in this laboratory a reproducible model of a Pneumococcal pneumonia. Using a large aerosol chamber we can induce a dose dependent incidence of lethal Pneumococcal pneumonia by administering aerosols of Type III Streptococcus pneumoniae. Studies to date have demonstrated an increased susceptibility and risk in both splenectomized populations of animals as well as those animals given experimental alloxan diabetes. The thrust of the research efforts for this coming year are twofold: One, to study sufficiently large groups of animals with hemi-splenectomy as well as other groups with induced splenosis. The creation of surgical hemi-splenectomy, we have done numerous times and this technique is easy. Some animals can retain viable amounts of recognizable spleen after mincing and reimplantation, but we have not been able to establish a uniformly reproducible model. The surgical manipulations of the spleen need to be studied to see if they offer a protective effect against the pneumonia and its subsequent sepsis. If so, this proposes the trial of such techniques in select groups of patients who might be at unacceptable risk for splenectomy. Currently underway is immuno-therapy as a prophylactic measure for splenectomized animals. Studies have shown that animals immunized against Pneumococcus prior to splenectomy retain identical resistance to induced bacteremia. All of the studies to date have involved intravenous injection of organism and no paper exists on the pulmonary system as a portal of entry. Our model involves the intramuscular injection of polyvalent vaccine followed by subsequent aerosol bacterial challenge in both control and splenectomized groups of animals.